What are the User_defined, Simple_color and Colorramp nodes used for?

Nodes are the essential building blocks in the Advanced interface to the Poser Material Room. They are the graphical representation of mathematical function calls, that is: calculation procedures which turn parameters (inputs) to a result (output).

Advanced

The Math group offers various nodes that can adjust and combine colors, images and other texture elements. This article discusses:

User_defined

Simple_color

Colorramp

which generate colors from value inputs. See for the overview of the Math group.

User_Defined

This node produces a color, that is: a three value RGB vector with each component between 0.0 and 1.0, from three independent input values.

When Color_Mode is set to RGB, the input values are just clipped to the 0..1 range and passed through. In the HSL or HSV modes, the inputs are clipped into the 0..1 range as well, and then translated to RGB colors. For instance, Hue=0 (or 1 or 2 or …) implies Red, Hue = 0.5 implies Cyan, Hue = 0,333 is Green. The input called Red contains Hue, Green contains Saturation and Blue contains Lightness or Value respectively.

In the HSL model, the Saturation starts at 0 with grey and mixes more and more pigment into it, until it’s saturated at S=1. The taint of grey is determined by the Lightness: 0 for full black to 1 for full white. So full red requires (0,1,any) for input. In the HSV model, Saturation determines the mixture with White (0 = white, 1 = full pigment) while Value determines the mixture with Black (0= black, 1 = full pigment). Full red requires (0,1,1).

Note: a color generated by this node will not be image-driven or color swatch-driven, but value-driven. As a consequence, it will not be pre-adjusted when renders are done with Gamma Correction ON (Poser 10, or Pro all versions), and results will look brighter than for color swatches representing the same color.

Simple_Color

This node produces… a simple color, as set by a color-swatch. Or a simply color-filtering of anything inputted to it.

This is useful when a single color is used multiple times in a materials node tree. Now it can be defined once and managed at one place. It’s simpler than using the User_Defined node, which requires three independent input values for R,G and B separately.

But there is another serious difference: when rendering under Gamma Correction, as available from Poser 10 and Pro 2010 and up, all color swatch defined colors are affected, but numerical settings as from User_Defined are not. This might give different results for a same color, when set in different ways.

Colorramp

This node produces a color from a four-point gradient, having the color-points set at 0%, 33%, 66% and 100%. The interpolated color is derived from the Input value, which should be between 0.0 and 1.0. I can plug in a greyscale image in here as well, to get it colored up.

Note: when rendering with Gamma Correction, the swatches will be pre-adjusted (darkened) but each at a different rate, and the Input-value will not. As a consequence, the resulting hues produced by this node will differ, depending on whether GC is used or not. See this article for details, and for eventual solutions.